Learning from the 2009 H1N1 Pandemic Response

Learning from the 2009 H1N1 Pandemic Response

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Daniel S. Miller MD, MPH

Director, International Influenza Unit Office of the Secretary

Office of Global Health Affairs Department of Health & Human Services

United States

Influenza Is a Significant Global Health Problem

• The influenza virus is CONTINUOUSLY circulating worldwide, infecting humans, birds, pigs, horses, and other animals.

• EVERY YEAR, the influenza virus continues to change and mutate genetically in the multi-species “mixing bowl”.

• EVERY YEAR, influenza sickens hundreds of millions, hospitalizes 3-5 million, and kills 250,000 – 500,000 people worldwide.

• EVERY YEAR, influenza causes large epidemics in temperate AND tropical zones.

• EVERY YEAR, influenza causes large epidemics in high, middle, AND low-income countries.

Global Influenza Surveillance

• Global influenza surveillance in clinics, hospitals, and laboratories around the world monitors the movement of the influenza virus and its genetic changes on a continuous basis.

• Global influenza surveillance is critical to monitoring and early warning of dangerous changes in the influenza virus (e.g. bird flu, emergence of H1N1).

• Global influenza surveillance is a critical tool for risk assessment and global response to influenza epidemics and pandemics.

The Role of Vaccines in Preventing Influenza Epidemics and Responding to Pandemics

• Vaccination is the most effective and cost-effective tool to prevent influenza epidemics.

• Vaccination is important to reduce illness and death in pandemics.

• Current technologies to produce influenza vaccine production are slow, complicated, difficult, and unpredictable.

• A high priority for vaccine production is to demonstrate that a vaccine is effective and safe before administering to a population.

Influenza Pandemics

• Periodically, the influenza virus changes suddenly such that the human population has little or no immunity.

• Global influenza pandemics have occurred for centuries, more recently in 1918, 1957, 1968, 2009.

• Influenza pandemics have been relatively mild (2009) and severe (1918).

• Influenza pandemics WILL occur again and are unpredictable.

• Global activities to improve pandemic preparedness have increased dramatically since 2005.

1. Patient 1

2. Patient 2

3. Recognition of potential match between Mexico and US viruses

4. US declares a public health emergency

5. WHO raises to Pandemic Phase 4

6. WHO raises to Pandemic Phase 5

Novel Swine-Origin Influenza A (H1N1) Virus Investigation Team. N Engl J Med 2009;10.1056/NEJMoa0903810

Confirmed Cases of Human Infection with Novel Influenza A (H1N1) with Known Date of Illness Onset, United States, March 28 – May 5, 2009

1 2 3 4 5 6

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Baseline (No Intervention)Dynamics

0 500 1000 15000

5,000,000

10,000,000

15,000,000

20,000,000

25,000,000

30,000,000

35,000,000

40,000,000

January 1 start date

WorldPoorLower MidUpper MidRich

Day number

Num

ber o

f cas

es

4

0

10

20

30

40

50

60

70

80

90

100

0

2000

4000

6000

8000

10000

12000

14000

Perc

ent P

osi

tive

Num

ber

of P

osi

tive S

peci

mens

Week Number

B A(Subtyping not performed)A(H1) A(H3)A(Unable to Subtype) A(2009 H1N1)Percent Positive

Virology 2008-10 Influenza Seasons in U.S.

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Outpatient visits for Influenza like Illness US: selected years

6

Influenza Activity October 31, 2009

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Pediatric Deaths Reported During Recent Influenza Seasons

Number of pediatric deaths

More pediatric deaths from flu reported in 2009-2010 season than in previous seasons

Season

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58% of children withunderlying condition

April 15, 2009 – January 5, 2010 (n=2280)

Underlying Conditions and Risk for 2009 H1N1 Hospitalization (Children)

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Underlying Conditions and Risk for 2009 H1N1 Hospitalization (Adults)

84% of adults withunderlying condition

April 15, 2009 – January 5, 2010 (n=4,139)

• 61 million (range: 43 m –89 m)

• 274,000 hospitalizations (range: 195,000 to 403,000)

• 12,470 deaths (range: 8,870 to 18,300)

• 1,280 deaths aged 17 and under (range: 910 to 1,880)

2009 H1N1 influenzaApril 2009 – April 2010

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Seasonality assumptions

0 50100

150200

250300

3500

0.2

0.4

0.6

0.8

1

1.2

New York SFSingapore SFSydney SF

t (assuming t0 = January 1)

Infe

ctiou

snes

s m

ultip

lier

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